Millions of activists around the world have rallied against seed giant Monsanto and the genetically modified food it produces.
The event - a social media-generated call to action against multinational corporations that produce genetically modified foods - marked the first such global, unified protest for this cause, organisers said.
Hundreds of people held marches on Saturday in Chicago, Los Angeles and New York. In Washington, protesters wearing yellow-and-black shirts lay on the pavement in a bee "die-in" outside Monsanto's offices.
Protests also took place in Amsterdam, Cairo, Durban, Melbourne, London, Stockholm and Vienna, among other places.
Genetically modified plants are grown from seeds that are engineered to resist insecticides and herbicides, add nutritional benefits or otherwise improve crop yields and increase the global food supply.
Most corn, soya bean and cotton crops grown in the United States today have been genetically modified. But critics say genetically modified organisms can lead to serious health conditions and harm the environment.
The use of GMOs has been a growing issue of contention in recent years, with health advocates pushing for mandatory labelling of genetically modified products even though the federal government and many scientists say the technology is safe.
The "March Against Monsanto" movement began just a few months ago, when founder and organiser Tami Canal created a Facebook page on February 28 calling for a rally against the company's practices.
"If I had gotten 3,000 people to join me, I would have considered that a success," she said. "It was empowering and inspiring to see so many people, from different walks of life, put aside their differences and come together today."
The group plans to harness the success of the event to continue its anti-GMO cause.
"We will continue until Monsanto complies with consumer demand. They are poisoning our children, poisoning our planet," she said. "If we don't act, who's going to?"
Monsanto, based in St Louis, Missouri, said that it respects people's rights to express their opinion on the topic, but maintains that its seeds improve agriculture by helping farmers produce more from their land while conserving resources such as water and energy.
The US Food and Drug Administration (FDA) does not require genetically modified foods to carry a label, but organic food companies and some consumer groups have intensified their push for labels, arguing that the modified seeds are floating from field to field and contaminating traditional crops.
The US Senate last week overwhelmingly rejected a bill that would allow states to require labelling of genetically modified foods.
The Biotechnology Industry Organisation, a lobbying group that represents Monsanto, DuPont and other makers of genetically modified seeds, has said that it supports voluntary labelling. But it says that mandatory labelling would only mislead or confuse consumers into thinking the products are not safe, even though the FDA has said there is no difference between GMO and organic, non-GMO foods.